Quiz: Do you really know VoIP?

Do you know how VoIP works? Put yourself to the test.

Do you know how VoIP works? Put yourself to the test. If your scores are not as high as you you'd like, read SearchUnifiedCommunications.com's How does VoIP work?: A technical guide to functional VoIP and make the VoIP grade.

  1. How many bits are in a conventional PCM voice sample? Answer

     

  2. How is a telephone call on the PSTN usually terminated? Answer

     

  3. Give the two basic components of a data message? Answer

     

  4. Every data frame or packet carries two components (at least) in the header. What are they? Answer

     

  5. In question 4, how does this differ from a PCM frame? Answer

     

  6. What is a CRC sequence used for? Answer

     

  7. Give at least two different ways the PSTN may setup a voice circuit. Answer

     

  8. List at least five drawbacks or challenges designers faced in making VoIP a reality. Answer

     

  9. List at least four tasks the gateway may do. Answer

     

  10. List at least four transmission media and formats that a media gateway should be able to support. Answer

     

  11. A media gateway interfaces a PSTN PCM bit stream. Give three types of traffic that may be transported in that bit stream, each requiring some sort of special handling. Answer

     

  12. Given an IP packet used for voice transport. Assume G.711 or G.726 coders. How many bytes (octets) can we expect in the payload? Answer

     

  13. Give some data you have learned about one-way delay. What is the one-way delay (in ms) that should not be exceeded as a design goal? Answer

     

  14. What one-way delay (in MS) should never be exceeded? Answer

     

  15. What would you say is the biggest contributor to one-way delay? Answer

     

  16. What is "look-ahead" used for? Answer

     

  17. There is buffer delay. What is its cause and it varies with the number of xxxxx in tandem? Answer

     

  18. What is one very obvious way to reduce delay? Answer

     

  19. On G.711 circuits, the lost packet rate objective is? Answer

     

  20. Give at least two ways to handle the presence of a lost packet. Answer

     

  21. What is the basic function of a media gateway controller? Answer

     

  22. Give at least three of the four signaling protocol options between an MGC and a media gateway. Answer

     

  23. Give a primary function of an MGC regarding delay using the H.323 protocol on a VoIP circuit. Answer

     

  24. Differentiate RTP and RTCP. Answer

     

  25. In the SIP protocol, what are end-users called?Answer

     

  26. What are the two modes with which a caller can set up a call with SIP? Answer

     

  27. In MGCP gateways are expected to execute commands sent by____. Answer

     

  28. Megaco (H.248) is a call-control protocol that communicates between a ____ and a____. Answer

     

  29. What are the two basic abstractions relating to the Megaco model? Answer

     

  30. A point-to-point connectivity must have at least ___ terminations. Answer

     

  31. How are terminations referenced in Megaco? Answer

     

Return to How does VoIP work?: A technical guide to functional VoIP.

This was first published in June 2006

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